(a) Field of the Invention
The present invention relates to carbonaceous material for a lithium-ion secondary battery. More particularly, the present invention relates to carbonaceous material for a lithium-ion secondary battery in which at least two exothermic peaks develop during differential thermal analysis of the carbonaceous material, and the generation peaks overlap to realize shoulders.
(b) Description of the Related Art
There are two basic types of carbonaceous material used in lithium-ion secondary batteries: crystalline graphite and amorphous carbon. Crystalline graphite offers the advantages of exceptional voltage flatness and high charge/discharge efficiency, but a charge/discharge efficiency decreases as a result of side reactions if many of the edges of the hexagonal crystalline graphite are exposed to electrolyte. With regard to amorphous carbon, although this material displays a high discharge capacity, it has a high irreversible capacity, low charge/discharge efficiency, and does not display a high level of voltage flatness.
There have been attempts at producing carbonaceous material using both crystalline graphite and amorphous carbon together to obtain the advantages of both these materials. However, the resulting carbonaceous material displays not only the advantages of crystalline graphite and amorphous carbon, but also all their disadvantages.